Brussels, 25 Mar 2004
Dairy industry waste is a potential source of biologically-produced polymers with commercial applications in packaging. WHEYPOL is seeking a cost-effective method to tap this abundant and sustainable resource.
Whey – the watery liquid separated from milk curd in the cheese-making process – has long been used as a source of protein concentrates and lactose for incorporation into food and animal feed. More recently, the drive to reduce man's dependence on finite fossil fuel reserves has encouraged efforts to exploit this abundant natural material as a starting point for the sustainable production of commercially applicable polymers and other chemicals.
The need for sustainable development is enshrined in the United Nations 1992 Rio declaration, and reiterated in the EU's 2002 Barcelona Council objective. At present, however, only around 10% of the raw materials used for production of organic chemicals in Europe and the USA derive from renewable resources. According to data published by the US National Research Council, this share could rise to 90% by 2090. It is thus an area in which continuing research is vital to the maintenance of Europe's competitive position.
Furthermore, the cost of the desalination needed in the production of lactose for classical applications is becoming prohibitively high. Annual output of whey in Europe is estimated to approach 50 million tonnes. Around 70% of this is currently processed, and the remainder discharged, often in an unregulated way. If consumption declines, the problem of disposing of this heavily polluting waste will inevitably increase. Identification of economically feasible alternative uses is therefore highly desirable from an environmental viewpoint.
In the Commission-supported WHEYPOL project, a group of ten academic and industrial partners is developing an integrated industrial process for microbially mediated synthesis of polyhydroxyalkanoates (PHAs), which are biodegradable polyesters that can replace conventional packaging plastics. They eventually decompose completely through naturally occurring microbiological mineralization, to yield only carbon dioxide and water. Consequently, neither their production nor their use or degradation has a negative ecological impact.
In addition to PHA production, the team is investigating the use of techniques such as melt blow extrusion and injection moulding for conversion of the polyesters into environment-friendly films and containers. These should be capable of meeting the constraints of the EU packaging and packaging wastes directive ( 62/94/EC ), as well as conforming to corresponding national regulations.
The WHEYPOL consortium is coordinated by Graz University of Technology in Austria, and includes institutes from Austria, Italy and three accession states: Poland, Slovenia and the Slovak Republic. The multidisciplinary team assembles expertise in microbiology and genetics, biotechnology and bioengineering, chemical engineering, and polymer chemistry, together with industrial experience in cheese production, plant construction and polymer processing.
Substantial progress achieved
WHEYPOL has made substantial progress since the start of the three-year initiative in December 2001. Following a literature survey, a number of promising micro-organisms were tested for growth and PHA production by the fermentation of whey and whey-derived nutritional media. Process parameters were then refined, and a reduced number of candidate organisms subjected to further study. The work led eventually to the selection of suitable bacteria that are sufficiently salt-tolerant to eliminate the need for desalination.
In addition to the fermentation itself, the upstream and stages of biomass separation, extraction and refining of the accumulated polyesters have been optimised. Two general approaches for isolation were determined:
- Use of non-toxic solvents in a method not previously described in literature; and
- A completely new approach that does not require any solvent.
After characterisation and testing, the refined polyesters may be blended with other polymers and/or with organic or inorganic fillers for use in the production of packaging materials or biodegradable nanocomposites for environmental and biomedical applications. Feedback from these trials is used to improve product quality by adapting the fermentation technology or other process steps.
"Biotechnological synthesis of polymers is mostly more expensive than production from mineral oil," points out WHEYPOL coordinator Professor Gerhart Braunegg. "Also, in aerobic processes such as ours, the carbon source accounts for around 50% of the total cost. In this respect, the reducing competitiveness of whey in its traditional markets could make our concept even more attractive.
"We tested a total of about 15 bacterial strains that use either lactose or hydrolysed lactose – that is glucose and galactose – from whey permeate. Our early experiments were performed in 100-ml flasks. Subsequently, we have scaled up to a 300-l bioreactor, which is already quite a large facility for a university. The polymer scientists in our consortium have confirmed that that the PHAs we can now produce are of very high quality, comparable to that of conventionally manufactured polyethylene terephthalate (PET) polyester resin.
"The next step would be to move from batch production to continuous processing, as a means of further reducing the costs of eventual implementation. From the data obtained to date, we can estimate that – if the initial investment is excluded – the cost per kilogram of produced PHA would be in the region of €0.90 to 1.50. My hope is that, on completion of this project, we can attract funding and partners to build a pilot plant that will enable us to build on this encouraging result."